Combustor cap assemblies have evolved over the years from a single fuel nozzle configuration to a multi-nozzle dry low NOx configuration with dual burning zone capability. The cost of combustion hardware has increased proportional to the mechanical complexity associated with the enhanced performance and lower emissions goals of modern combustion systems.
The function of the cap primary nozzle cup assembly is to deliver fuel and air from the fuel nozzle and end cover assembly to the primary zone of the combustor. Air and fuel pass axially through each primary nozzle cup. Air passes through the sidewalls of each primary cup in a radially inward direction, providing cooling for the cup wall. Air also passes through multiple apertures in the cap impingement plate thereby cooling the plate and supplementing the total cap airflow.
The current dry low NOx combustor cap configuration consists of many sheet metal and machined parts in a welded and brazed assembly. The disadvantages of this assembly are:
(1) The cost of manufacturing of multiple parts continues to increase;
(2) Assembly costs are high as many processes are involved; and
(3) Manufacturing cycle time is excessive and precludes production of a volume of assemblies in a limited capacity shop.